In classical magnetic resonance imaging (MRI) techniques, the proton density of physical tissue characteristics is sensed to discriminate between healthy and diseased tissue. In the case of tissue that is in motion, such as the human heart, diseased portion of the heart are optimally detected by assessment of wall motion of a heart chamber and wall thickness during this cardiac cycle. One technique which attempts to do the foregoing is the use of ultrasound (referred to as "echo" in the industry); and to some extent other techniques are X-ray computed tomography, contrast ventriculography, nuclear scanning, and finally classical or conventional MRI.
All these methods suffer from the same critical limitation: the inability to visualize and to track the same portion of the ventricular myocardium throughout the cardiac cycle. For instance, all tomographic imaging methods visualize a thick slice of space through which the myocardium moves during the cardiac cycle. Thus images taken at different instants in the heart cardiac cycle are actually different segments of the myocardium of the heart. The movement of the heart during the cardiac cycle is complex and involves displacement along all three axes.
One technique involving physical invasion of the heart itself to detect the foregoing has been to surgically implant markers. In addition to the invasiveness of the above technique, it does not adequately measure needed parameters.
MRI has been used for the measurement of blood flow in the human body but with limited success.